At a superficial glance the Viper is quite distinct from our other Snakes. Instead of the long, gracefully tapered body of these, the Viper is short and thick in the body with a short tail. So far as the length is concerned, the average Viper is less than two feet. A few exceptionally large females have been recorded measuring two feet eleven inches; but the female is always slightly longer than the male—usually about an inch more. Two feet three inches may be regarded as the ordinary maximum for a female. The head is flatter above, and it broadens behind the eyes, so that it is very distinct from the body; further, the shields on the head are very much smaller than the corresponding plates of the Grass Snake. The iris of the eye is coppery-red, and the pupil is vertical—which usually denotes nocturnal habits, but the Viper is active by day as well as by night, and is fond of basking in the sunshine.
Respecting colour, there is a considerable range of variation, much of it sexual; but, generally speaking, it may be said to be some tint of brown, olive, or grey, and this ground colour may be so dark that the darker markings are scarcely perceptible on a cursory view. Along the sides there are whitish spots, sometimes reduced to mere dots. The brown, red-brown, or olive males have black markings; the grey or whitish males are marked with brown or black, and have the underside black. The throat is black, or whitish with scales spotted or edged with black.
The females if brown or brick-red have dark brown or red markings; olive females have brick-red bands or spots. The yellowish-white chin and throat are sometimes tinged with red. The eyes of the female are smaller than those of the male.
The markings are subject to a good deal of variation as well as the ground colour. The usual wavy or zigzag line down the centre of the back, with a series of spots on either side, may be broken up into oval spots; and the characteristic pair of dark bars on the head may form either a Λ or an Χ. The broad shields which cover the lower surface may be grey, brown, bluish, or black, or bluish with triangular spots of black, sometimes with white dots along the margins. Below the end of the tail the colour is yellow or orange. Specimens have been recorded almost entirely of a rich black, the excepted portion being the whitish underside of the head and throat.
The usual haunts of the Viper are sandy heaths, dry moors, the sunny slopes of hills and hedgebanks, bramble clumps, nettle beds, heaps of stones and sunny places in woods; but we have also found it in heathy and grassy places that were distinctly and permanently wet. For food they appear to prefer small mammals such as mice, shrews and voles, young weasels; but also take birds, lizards, slow-worms, frogs, newts, and large slugs. The young subsist for a time on insects and worms.
The Viper retires in autumn to a hollow under dry moss among the heather, under faggot stacks or into the discarded and leaf-covered ground nests of birds. They reappear about April, and may then be seen coiled on a sunny bank, apparently more concerned to absorb heat than to find food. They pair at this season, and the young (varying from five to twenty) are born in August or September. In this species, again, the eggs are retained until fully developed, and when the young see the light they are coiled up tightly in a thin, transparent membrane, which usually breaks during the process of birth. They measure from six to eight inches, and are at once independent.
The hoary old legend about the mother Viper opening her jaws to afford sanctuary to her young in time of danger has probably arisen from some occasional acts of cannibalism. It presupposes what is not true of any of our reptiles—that the young remain with their parent. They all begin life equipped for independence, and act accordingly.
The Viper is not so amenable to a life of captivity as our other Snakes. It is not amiable, indeed its temper may be described as short and sulky, which it displays by refusing all offers of food; most captive Vipers die of starvation, the "hunger strike" being their effective protest against the deprivation of liberty. On being captured they are always ready to bite; but in a state of freedom the Viper is not the aggressive monster that is popularly supposed. It seems to depend largely upon its inactivity for escaping observation, but when it knows it has been discovered its immediate impulse is to seek cover. Accidents from Viper bites are rare in this country, where people go about well shod, and there are very few cases of authenticated death from this cause. On the Continent, however, such cases are frequent; and it is suggested that in the warmer parts of Europe, where bare feet are more numerous, the Viper's venom may also be more active than it is here. It is the toes or fingers that are most likely to be bitten, for the Viper's mouth is not large enough to enable it to bite the larger parts. The mechanism by which the poison is introduced into the blood of its victim has been briefly described on [page 146].
